The present invention relates to variable displacement axial piston pumps and pertains particularly to a variable displacement axial piston pump having displacement control means which are automatically operative to maintain and infinitely vary displacement of said pump.
Variable displacement pumps are often utilized in earth moving and other heavy duty machinery because pump flow and system pressure can be varied to meet system demands. Such variable displacement pumps are often equipped with pressure compensator controls for controlling or varying pump output pressure in response to system pressure.
A number of control systems are known which rely on load pressure of the system for controlling the displacement of the pump. However, these prior art systems also fail to include sufficient variables to insure precise and continuous control of the displacement.
The prior art is exemplified by the following patents: U.S. Pat. No. 2,892,312 which issued to J. R. Allen et al from an application filed on Jan. 27, 1958, and which is assigned to Deere & Company; U.S. Pat. No. 3,738,111 which issued to E. H. Fletcher from an application filed on Nov. 11, 1971, which is assigned to Deere & Company; and U.S. Pat. No. 3,444,689 which issued to T. Budzich on May 20, 1969 from an application filed on Feb. 2, 1967, and which is assigned to The Weatherhead Company.
Accordingly, this invention resides in a pump assembly having control means for varying the displacement of the pump in response to load pressure on the pump.